How to Design a GeoDB GEOG 419/519: Advanced GIS

© Arthur J. Lembo, Jr. Cornell University

Key is asking the right questions: • How can GIS technology be implemented to streamline existing functions or change the way we achieve a goal • What data will benefit the organization the most? • What data can be stored? • Who is responsible for maintaining the database? © Arthur J. Lembo, Jr. Salisbury University

Truths about Design • Time-consuming • No end-use applications • If not done:

10000 9000 8000 7000 6000

Production

5000 4000 3000

Implementation

2000 1000 0

Concept

Concept

– Database may not meet requirements – Can end up with duplicate, missing, or unnecessary data – Lack of necessary management © Arthur J. Lembo, Jr. techniques Salisbury University

Analysis

Design

Design

Data Collection

Implementation

Objectives of Design • Design should define goals, identify, analyze, and evaluate design alternatives, and create implementation plan • Investment of time and money up front saves even more time and money later • A functional, well-organized database: – – – – –

Satisfies organizational objectives Contains all necessary data Accommodates different views of the data Distinguishes maintenance apps from user apps Organizes data so that different users access the same data © Arthur J. Lembo, Jr. Salisbury University

© Arthur J. Lembo, Jr. Salisbury University

Design Guidelines • • • • • • • • • •

Involve users Take it one step at a time Build a team Be creative Create deliverables Keep organizational goals and objectives in focus Do not add detail prematurely Document carefully Be flexible Plan from you model © Arthur J. Lembo, Jr. Salisbury University

•

Create from scratch: create schema for features datasets, classes, and attribute tables. • Import Existing Data: a schema is created, and existing data in imported in. • Use CASE tools: computer aided software engineering principles and GUIs can be used to create a geodatabase • THIS IS HOW TO BUILD A COMPUTER DATABASE, BUT DOESN’T MEAN ITS OF ANY USE – for this you need good database © ESRI, Building Geodatabases design © Arthur J. Lembo, Jr. Salisbury University

Steps in Building a GeoDB • • • • •

Model the user’s view of data Define objects and relationships Select geographic representation Match to geodatabase elements Organize geodatabase structure

© Arthur J. Lembo, Jr. Salisbury University

Designing GIS Databases • • • • •

Model the users’ view Define entities and their relationships Identify representation of entities Match to GIS data model Organize into geographic data sets The first three steps develop the conceptual model, classifying features based on an understanding of the data required to support the organization’s functions, and deciding their spatial representation. The last two steps develop the logical model, matching the conceptual models to ArcGIS geographic data sets © Arthur J. Lembo, Jr. Salisbury University

The Data Model • Data Model is a formal definition of the data required in a GIS. Types include: – Structured List – Entity Relationship Diagram

• Purpose of the data model is to ensure that the data is identified and described in a completely rigorous and unambiguous fashion

© Arthur J. Lembo, Jr. Salisbury University

Example Structured List © ESRI

Feature

Layer

Type

Prim. Attr.

Owner

Landuse

LU

Poly

LUID

Planning

Soils

Soil

Poly

SoilID

na

Elevation

DEM

Raster na

na

Hydrography

Hydro

Line

ID

DEC

Roads

CL

Line

ID

Eng.

Buildings

Bldg

Poly

ID

Eng.

Parcels

Parcel

Poly

SBL

Assessor

© Arthur J. Lembo, Jr. Salisbury University

Model the User’s View • Identify the functions that support the organization’s goals and objectives • Identify the data required to support the functions • Organize the data into logical sets of features • Define an initial implementation plan • Identify organizational functions © Arthur J. Lembo, Jr. Salisbury University

© Arthur J. Lembo, Jr. Salisbury University

Define Entities and Relationships • Identify and describe entities • Identify and describe the relationships among these entities • Document the entities and relationship with UML diagrams • Create statements about how the system works then evaluate those statements in terms of entities and relationships © Arthur J. Lembo, Jr. Salisbury University

© Arthur J. Lembo, Jr. Salisbury University

The Nature of Geographic Data • Geographic data has been described as: – Object - a thing that can be seen or touched. – Entity - objects or things to be included in a database – Feature - the make, shape, form or appearance of a person or thing. Term that derives itself from cartography (features on a map) – Attribute - characteristics of the entities © Arthur J. Lembo, Jr. Salisbury University

Identify the representation of entities • Is the feature represented on a map? • Is the shape of a feature important? • Is the feature best accessed through its relationship with another feature? • Will the feature have different representations at different scales?

© Arthur J. Lembo, Jr. Salisbury University

© Arthur J. Lembo, Jr. Salisbury University

Classical Entities and Spatial Component

© ESRI

Entity Entity Attributes

Spatial Component

Street (name, number)

line (coordinates, topology)

Soil Zone (name, perm.)

polygon (coordinates, topology)

Well (type, date tested)

point (coordinates)

© Arthur J. Lembo, Jr. Salisbury University

E-R Diagram Platform

Side Number

Part of

Station © Arthur J. Lembo, Jr. Salisbury University

Name Zone

Spatial Relationships Spatial Relationship

Verbs

Connectivity

Connect, link

Contiguity

Adjacent

Containment

Contained

Proximity

Nearest

Coincidence

Coincident © Arthur J. Lembo, Jr. Salisbury University

Symbol

Considerations in Modeling Geography in an E-R Diagram • Correct Identification and Definition of Entities • Defining a Corresponding “Spatial” Entity for Each “Traditional” Entity • Recognition of Multiple Instances of Geographic Entities – time and scale – Represented by: entity simple, entity spatial, entity time © Arthur J. Lembo, Jr. Salisbury University

Representation of Spatial Objects Object Name

Object (entity) Spatial Object

Associated Spatial Object Type

G

T

XY Coordinate system © Arthur J. Lembo, Jr. Salisbury University

Topology: point, line, polygon

Modeling Spatial Relationships ENTITY

RELATIONSHIP

ATTRIBUTE © Arthur J. Lembo, Jr. Salisbury University

Developing a Spatial E-R Diagram • Is Derived From Needs Assessment • Relationships Determined from Application Descriptions Soil Sample Point

G

T

Contained In /Contains

© Arthur J. Lembo, Jr. Salisbury University

Farm Plot Polygon

G

T

Match to a GeoDB model • Determine appropriate geodb representation for entities – Spatial type = point • Unconnected – point feature • Connected – simple junction • Connected with internal topology – complex junction

– Spatial type = line • Stand-alone line = line feature • Line in a system = simple edge • Line with connected sections = complex edge

– Areas = polygon feature (with potential planar topology) – Objects = objects © Arthur J. Lembo, Jr. Salisbury University

© Arthur J. Lembo, Jr. Salisbury University

Physical Design • Logical Design Performed Independent of Physical Design • Must Now Move Logical Design to Physical Design • Physical Design Example (ARC/INFO, geodatabase):

© Arthur J. Lembo, Jr. Salisbury University

Conceptual vs. Physical Design Temp Logger G

Point

LINKS with T

Line

Physical Design Stream

PAT

BND

AAT

Stream Segment G

T

Stream

Reach Order

INFO

TIC

NAT

TempLog

ID

© Arthur J. Lembo, Jr. Salisbury University

History

ID Date Temp

Organize into Geographic Datasets • Assign entities to feature classes and subtypes – Feature classes vs. subtypes

• Group related sets of features into geometric networks or planar topologies – Simple edges & junctions, complex edges & junctions – geometric network – Need space-filling and no overlapping – planar topology

• Organize feature classes and datasets into geodb’s © Arthur J. Lembo, Jr. Salisbury University

© Arthur J. Lembo, Jr. Salisbury University